<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<meta http-equiv="X-UA-Compatible" content="IE=edge">
	<meta name="viewport" content="width=device-width, initial-scale=1, minimum-scale=1,maximum-scale=1, user-scalable=no" />

	<title>rem自适应</title>
	<link rel="stylesheet" href="">
	<style>
		html { 
			font-size: calc(100vw / 3.75); 
		}
	</style>
</head>
<body>
	<span>哈哈哈哈h</span>
</body>
<!-- 
我们只需要监听resize事件即可
document.documentElement.style.fontSize = document.documentElement.clientWidth/3.75 + 'px';
$(window).on('resize', function() {
   document.documentElement.style.fontSize = $(document.documentElement).width()/3.75 + 'px';
})
 -->
</html>